code: def test_change_layer(self):
      test_layer = heatmap_layer([(1.0, 2.0), (3.0, 4.0)])
      m = maps.Map()
      assert m.get_state()["layers"] == []
      m.layers = [test_layer, test_layer]
      assert m.get_state()["layers"] == [
          "IPY_MODEL_" + test_layer.model_id,
          "IPY_MODEL_" + test_layer.model_id,
      ]
  
file_path: gmaps/gmaps/tests/test_maps.py
imports: import unittest
  import traitlets
  from ..None import maps, heatmap_layer
label_desc: Use image node_id 3 for calling the Map obj's underlying member method code with example usage: obj.test_change_layer() without return types